If you keep getting the the message that your server is down,
than your webhost probably does not allow you to use UDP socket
connections... If you have any other, more liberal hosts, try installing
it there, as I guess the problem is host related...
You can see a working preview for your server here:
http://www.student.ru.nl/bennitebeek/tim/si2/gits.php
So it's not a problem with your gameserver. It's your webhost not
allowing you to make UDP socket connections, or they are not made
properly, which both result in the server down message... =\
Try asking your webhost to allow these connections, or host the script
on a different host...

Tim